All of the robot kits and electronics experiments we make here at Bot-In-a-Box are open-source, so you're free to make them yourself with whatever parts you may have available.
That being said, if you're looking for a convenient way to pick up the parts you need for a certain project or robot kit, you've come to the right place!
Your shopping list will contain links to eBay listings for the parts you need. Please see Bot-In-a-Box's Affiliate Link Disclosure for more information regarding these links.
It seems to be rather difficult to find a reasonably-priced Pi Zero W computer board on eBay these days. The eBay link selected when you add one to your shopping list is arguably more expensive than it needs to be (especially for Canadian customers). However, it comes with pre-soldered header pins, and it's even more difficult to find that style of board online.